Hollow thread film cartridge, hollow thread film module using the cartridge, and tank type filter

ABSTRACT

A hollow fiber membrane cartridge wherein a cartridge head and a bottom ring are connected and fixed to each other by means of a plurality of rods or pipes, the hollow portion at the end of each hollow fiber membrane on the cartridge head side is open, the hollow portion at the end of each hollow fiber membrane on the bottom ring side is sealed, and a plurality of through-holes are provided in an adhesion and fixation layer on the bottom ring side and are located in a bundle of the hollow fiber membranes.

TECHNICAL FIELD

[0001] The present invention relates to a filtration cartridge usinghollow fiber membranes which is set in a tank type filtration apparatus,a rack type filtration apparatus or an immersion type filtrationapparatus, in which filtration is carried out under pressure or bysuction. More particularly, the present invention relates to a hollowfiber membrane cartridge used in a filtration apparatus for removingturbidity and bacteria from a large volume of raw water such as riverwater, lake water, underground water, sea water, life waste water orindustrial waste water or a filtration apparatus for solid-liquidseparation in activated-sludge treatment; and a module for rack typefiltration apparatus, or a tank type filtration apparatus, which usessaid hollow fiber membrane cartridge.

BACKGROUND ART

[0002] JP-A-61-153104 discloses, as a conventional cartridge usinghollow fiber membranes, a cartridge having the following structure: aplurality of hollow fiber membranes are accommodated in a cylindricalcasing, both ends of each hollow fiber membrane are fixed to thecylindrical casing in the upper and lower adhesion and fixationportions, respectively, and the cylindrical casing is a casingintegrally molded so as to extend to the upper and lower ends of thehollow fiber membranes. The hollow portions of a large number of thehollow fiber membranes are open in the upper adhesion and fixationportion of the cartridge but are sealed in the lower adhesion andfixation portion, and an adhesive layer in the lower adhesion andfixation portion has a plurality of through-holes. A gas chambersurrounded by the cylindrical casing is formed under the lower adhesionand fixation portion.

[0003] This hollow fiber membrane cartridge is for filtration underexternal pressure and is used after being set in a filtration column.When materials to be filtered are accumulated on the outer surfaces ofthe membranes, the filtering capability of the membranes is diminished,and therefore a washing procedure for removing the accumulated materialson the surfaces of the membranes is carried out after filtration for adefinite time.

[0004] For this washing procedure, a method called gas bubbling isadopted which comprises introducing a gas into the hollow fiber membranecartridge through its lower portion in a filtration column filled withraw water, and vibrating the hollow fiber membranes in a gas-liquidmixed fluid to peel off the accumulated materials on the surfaces of themembranes.

[0005] However, in the hollow fiber membrane cartridge, gas bubbling hasinsufficient washing effect in some cases because both ends of eachhollow fiber membrane are fixed to the cylindrical casing, so that theextension and vibration of the hollow fiber membranes are limited. Thisphenomenon is remarkable and causes troubles in a long-term filtrationoperation, particularly when the diameter of the cartridge is large.

[0006] On the other hand, JP-A-2000-157846 has proposed a hollow fibermembrane cartridge comprising a cartridge head and a bottom ring towhich the end of a bundle of hollow fiber membranes is adhered andfixed, wherein the cartridge head and the bottom ring are not connectedand fixed to each other, and a plurality of through-holes for gasintroduction are provided in the adhesion and fixation layer of thebottom ring. This hollow fiber membrane cartridge has no cylindricalcasing and hence is advantageous in that the extension and vibration ofthe hollow fiber membranes are not limited during gas bubbling, so thatit is easy to peel off suspended materials accumulated on the surfacesof the membranes and to discharge the suspended materials peeled off,from the cartridge.

[0007] However, in this hollow fiber membrane cartridge, the feed rateof a gas must be limited in order to prevent the bundle of the hollowfiber membranes from bending due to the lift of the bottom ring duringthe gas bubbling. On the other hand, when the gas bubbling is repeatedlyconducted for a long period of time by the use of a large volume of agas in order to obtain a sufficient washing effect, the bundle of thehollow fiber membranes is repeatedly bent, so that the hollow fibermembranes are cut in some cases. Therefore, in either case, a long-termfiltration operation is difficult to carry out stably.

[0008] JP-A-10-137552 discloses a cartridge in which an upper adhesionand fixation layer and a lower adhesion and fixation layer are connectedto each other by locating a supporting column in the center of a bundleof membranes. This cartridge makes it possible to avoid the buckling ofthe bundle of hollow fiber membranes during gas bubbling by the locationof the supporting column in the center but involves the followingproblems: insufficient washing effect is obtained because of the lowefficiency of contact between bubbles and the hollow fiber membranes,the cartridge has insufficient resistance to a torsion produced duringhandling or gas bubbling, and the cartridge is difficult to handlebecause its upper and/or lower adhesion and fixation portion should beheld when the cartridge is carried.

[0009] In addition, WO98/28066 discloses a cartridge obtained bysurrounding the periphery of a bundle of membranes with a perforatedcage-like member. This cartridge is disadvantageous in that since only asmall washing effect can be obtained therein because the vibration ofthe hollow fiber membranes during gas bubbling is limited, a largevolume of gas needs to be introduced thereinto in order to obtain asufficient washing effect.

DISCLOSURE OF THE INVENTION

[0010] The present invention is intended to provide a hollow fibermembrane cartridge which makes it easy to peel off suspended materialsaccumulated on the outer surfaces of hollow fiber membranes, by theintroduction of a small volume of a gas by extending and/or vibratingeach hollow fiber membrane as much as possible at the time of washing bygas bubbling, permits easy discharge of the peeled-off suspendedmaterials from the hollow fiber membrane cartridge, and makes itpossible to carry out a long-term stable filtration operation; and toprovide a module for filtration apparatus or a filtration apparatus,which uses said hollow fiber membrane cartridge.

[0011] The present inventors earnestly investigated in order to solvethe problems described above, and consequently found that a cartridgeobtained by connecting and fixing a cartridge head and a bottom ring toeach other by means of a plurality of rods or pipes is suitable for theabove purpose, and that employment of hollow fiber membranes having aspecific modulus in tension makes it possible to obtain a sufficientwashing effect by using a small volume of a gas. On the basis of thisfinding, the present invention has been accomplished.

[0012] That is, the present invention is as follows.

[0013] (1) A hollow fiber membrane cartridge comprising a bundle of aplurality of hollow fiber membranes, both ends of which are fixed byadhesion in adhesion and fixation layers, respectively, a cartridge headfixed at the periphery of the bundle at one end so as not to permit thepassage of liquid either in or out, and a bottom ring fixed at theperiphery of the bundle at the other end so as not to permit the passageof liquid either in or out, which is characterized in that saidcartridge head and said bottom ring are connected and fixed to aplurality of rods or pipes, the hollow portion at the end of each hollowfiber membrane on the cartridge head side is open, the hollow portion atthe end of each hollow fiber membrane on the bottom ring side is sealed,and a plurality of through-holes are provided in the adhesion andfixation layer on the bottom ring side and are located in the bundle ofthe hollow fiber membranes.

[0014] (2) A hollow fiber membrane cartridge according to the above item(1), wherein the end of said bottom ring juts out beyond the ends of thehollow fiber membranes.

[0015] (3) A hollow fiber membrane cartridge according to the above item(1) or (2), wherein said cartridge head has a collar at its periphery.

[0016] (4) A hollow fiber membrane cartridge according to any one of theabove items (1) to (3), wherein said rods or pipes are located near theperiphery of the bundle of the hollow fiber membranes.

[0017] (5) A hollow fiber membrane cartridge according to the above item(4), wherein said rods or pipes are connected and fixed to saidcartridge head and said bottom ring by adhesion to them together withthe hollow fiber membranes in the adhesion and fixation layers.

[0018] (6) A hollow fiber membrane cartridge according to any one of theabove items (1) to (5), wherein the hollow fiber membranes have waves.

[0019] (7) A hollow fiber membrane cartridge according to any one of theabove items (1) to (6), wherein the modulus in tension of the hollowfiber membrane is less than 90 MPa and not less than 10 MPa.

[0020] (8) A hollow fiber membrane cartridge according to the above item(7), wherein the modulus in tension of the hollow fiber membrane is notmore than 70 MPa and not less than 10 MPa.

[0021] (9) A hollow fiber membrane cartridge according to any one of theabove items (1) to (8), wherein the hollow fiber membranes are in aslacked state and the rate of slacking is not more than 10% and not lessthan 0.1%.

[0022] (10) A hollow fiber membrane cartridge according to any one ofthe above items (1) to (9), wherein said plurality of through-holesprovided in the adhesion and fixation layer on the bottom ring side arelocated so that the hollow fiber membranes are present among thethrough-holes.

[0023] (11) A hollow fiber membrane cartridge according to any one ofthe above items (1) to (10), wherein said plurality of through-holesprovided in the adhesion and fixation layer on the bottom ring side havean inside diameter of 2 to 30 mm.

[0024] (12) A hollow fiber membrane cartridge according to any one ofthe above items (1) to (11), wherein an adhesive constituting saidadhesion and fixation layers is a urethane resin having such acharacteristic that its hardness is 70D to 30D in a working temperaturerange.

[0025] (13) A module for rack type filtration apparatus using a hollowfiber membrane cartridge according to any one of the above items (1) to(12).

[0026] (14) A tank type filtration apparatus using a hollow fibermembrane cartridge according to any one of the above items (1) to (12).

[0027] (15) A tank type filtration apparatus according to the above item(14), wherein said hollow fiber membrane cartridge is supported in asuspended state.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a sectional illustration showing one embodiment of thehollow fiber membrane cartridge of the present invention supported in asuspended state in a tank type filtration apparatus.

[0029]FIG. 2 is an enlarged view of the principal part showing thestructure of the bottom ring adhesion and fixation portion of the hollowfiber membrane cartridge shown in FIG. 1.

[0030]FIG. 3 is a schematic illustration of the known hollow fibermembrane cartridge.

[0031]FIG. 4 is a sectional illustration showing one embodiment of thehollow fiber membrane cartridge of the present invention fixed bysuspension from a treated water header piping in a tank type filtrationapparatus.

[0032]FIG. 5 is a sectional illustration showing one embodiment of ahousing constituting a module used in a rack type filtration apparatus.

[0033]FIG. 6 is a sectional illustration showing one embodiment of amodule used in a rack type filtration apparatus, namely, a moduleobtained by accommodating the hollow fiber membrane cartridge of thepresent invention in the housing shown in FIG. 5.

[0034]FIG. 7 is a sectional illustration showing one example of thelocation of through-holes in the bottom ring adhesion and fixationportion of the hollow fiber membrane cartridge.

[0035]FIG. 8 is a sectional illustration showing another example of thelocation of through-holes in the bottom ring adhesion and fixationportion of the hollow fiber membrane cartridge.

[0036]FIG. 9 is an enlarged illustration of the principal part showingone embodiment of the connection of a cartridge header to the piping ofan apparatus in FIG. 4.

[0037]FIG. 10 is an enlarged illustration of the principal part showingone embodiment of the connection of a cartridge header in the case ofFIG. 8 to the piping of an apparatus.

[0038]FIG. 11 is an enlarged illustration of the principal part showingone embodiment of the connection of a cartridge header to the piping ofan apparatus used in immersion type filtration carried out by directimmersion in raw water followed by filtration by suction.

BEST MODE FOR CARRYING OUT THE INVENTION

[0039] Embodiments of the present invention are concretely explainedbelow with reference to the drawings.

[0040]FIG. 1 is a sectional illustration showing one embodiment of thehollow fiber membrane cartridge of the present invention supported in asuspended state in a tank type filtration apparatus. FIG. 2, FIG. 7 andFIG. 8 are illustrations for explaining the structure of the bottom ringadhesion and fixation portion of the hollow fiber membrane cartridge.FIG. 6 is a sectional illustration showing one embodiment of the hollowfiber membrane cartridge in a module used in a rack type filtrationapparatus. FIGS. 9 to 11 are sectional illustrations showing embodimentsof the connection of a cartridge header to the piping of an apparatus.

[0041] The hollow fiber membrane cartridge 4 of the present invention iscomposed of a large number of hollow fiber membranes 3 a, connectingpipes 3 b, an adhesion and fixation layer 11, a cartridge head 12, anadhesion and fixation layer 14 and a bottom ring 13.

[0042] At one end of a bundle of the hollow fiber membranes 3 a and oneend of each connecting pipe 3 b, the hollow fiber membranes areintegrally bonded to one another with an adhesive and are integrallyattached to the inside of the cartridge head 12 to form the adhesion andfixation layer 11. The ends of the hollow fiber membranes 3 a on thecartridge head 12 side are open.

[0043] At the other end of the bundle of the hollow fiber membranes 3 aand the other end of each connecting pipe 3 b, the hollow fibermembranes are integrally bonded to one another with an adhesive and areintegrally attached to the inside of the bottom ring 13 to form theadhesion and fixation layer 14. The ends of the hollow fiber membranes 3a on the bottom ring 13 side are sealed. As shown in FIG. 2, a pluralityof through-holes 14 a are formed in the adhesion and fixation layer 14in order to introduce raw water or a gas for washing into the bundle ofthe hollow fiber membranes and bring the raw water or the gaseffectively into contact with the outer surface of each hollow fibermembrane.

[0044] The diameter of the hollow fiber membrane cartridge 4 is 30 mm to800 mm, preferably 80 mm to 800 mm. The length of the hollow fibermembrane cartridge 4 ranges preferably from 300 mm to 3,000 mm.

[0045] In the present invention, the cartridge head 12 and the bottomring 13 are connected and fixed to each other by means of two or morerods or pipes. A cylindrical casing such as that of the conventionalcartridge shown in FIG. 3 is not present at the periphery of the bundleof the hollow fiber membranes 3 a between the cartridge head 12 and thebottom ring 13, and substantially throughout this range, the hollowfiber membranes are exposed. Although a method for connecting thecartridge head and the bottom ring to each other by the plurality of therods or pipes is not particularly limited, the rods or pipes arepreferably fixed by embedding the rods or pipes in the adhesion andfixation layers as described above.

[0046] When the cartridge head 12 and the bottom ring 13 are notconnected and fixed to each other, increasing the flow rate of a gas orwater in washing by gas bubbling or flushing lifts the bottom ring tobend the bundle of the hollow fiber membranes, when the flow rateexceeds a definite rate, though the definite rate is dependent on thestrength of the hollow fiber membranes, the number of the hollow fibermembranes and the length of the hollow fiber membranes.

[0047] When only one rod or pipe is used for the connection andfixation, a stress is centered at one point and moreover, the cartridgeis insufficient in resistance to bending or twisting in the lateraldirection. This phenomenon is remarkable and causes troubles in along-term filtration operation, particularly when the diameter of thecartridge is large.

[0048] As to the size of the rods or pipes for the connection andfixation, the equivalent diameter of the rods or pipes ranges from 2 mmto 30 mm. Here, the equivalent diameter is defined as 4×(sectional areaof flow path)/(circumference). The shape of the cross-section of therods or pipes for the connection and fixation is selected from polygons(e.g. triangle, tetragon and hexagon), a round shape, an oval shape, afan shape, a C shape, a star shape, etc. The rods or pipes preferablyhave in particular a round shape of cross-section. The number of therods or pipes is 2 to 30 though it is dependent on the sectional area ofthe cartridge and the number of fibers.

[0049] Although the size and number of the rods or pipes should bedetermined so that the rods or pipes can withstand a mechanical loadapplied at the time of use or handling, they are preferably minimized asmuch as possible because when the size or number determined isexcessive, the rods or pipes occupy a large area, resulting in a smallmembrane area per unit area. For the minimization, the location of theplurality of the rods or pipes is an important factor. That is, the rodsor pipes are preferably located so that they can uniformly receive aforce applied from below during gas bubbling or flushing. For example,the rods or pipes are preferably located at regular intervals at theperiphery of the bundle of fibers or located so as to be dispersed inthe bundle of fibers. Particularly when the rods or pipes are located inthe vicinity of the periphery of the bundle of fibers, the cartridge canbe handled by holding the rods or pipes, so that the handleability ismarkedly improved. Furthermore, a sufficient mechanical strength againstbuckling and torsion can be assured even if the rods or pipes occupyonly a small area. Therefore, it is especially preferable to locate therods or pipes in the vicinity of the periphery of the bundle of fibers.The term “the vicinity of the periphery” used here means an innerportion of the bundle of fibers which extends over a distance ofone-fourth the diameter of the bundle of fibers from the peripherysurface of the bundle of fibers.

[0050] For fixing the rods or pipes for the connection and fixation tothe adhesion layer 11 on the cartridge header side and the adhesionlayer 14 on the bottom ring side, the following methods, for example,can be adopted: a method of fixing the rods or pipes with an adhesivetogether with the bundle of the hollow fiber membranes; a method ofpreviously making holes in the cartridge header and the bottom ring inorder to insert the rods or pipes for the connection and fixation intothe holes, inserting the rods or pipes for the connection and fixationinto the holes, and adhering and fixing the rods or pipes together withthe bundle of the hollow fiber membranes; and a method of fixing therods or pipes at the peripheries of the cartridge header and the bottomring. The methods of adhering and fixing the rods or pipes to theadhesion and fixation layers together with the hollow fiber membranesare suitable.

[0051] As the hollow fiber membrane 3 a used in the present invention,reverse osmosis membranes, nano-filtration membranes, ultrafiltrationmembranes and microfiltration membranes can be used from the viewpointof pore size.

[0052] A flexible hollow fiber membrane is preferably chosen as thehollow fiber membrane 3 a because it brings about a sufficient washingeffect even at a relatively small volume of a gas. Specifically, themodulus in tension of the hollow fiber membrane is preferably less than90 MPa and not less than 10 MPa, more preferably not more than 70 MPaand not less than 10 MPa, still more preferably not more than 60 MPa andnot less than 10 MPa. The modulus in tension is a value obtained byusing the following measuring method and is a value measured for themembrane in use, namely, the membrane in a wet state. In detail, themodulus in tension was determined by pulling the membrane with a tensiletester under conditions of a distance between chucks of 50 mm and a rateof pulling of 200 mm/min, determining a load at an elongation of 100% byextrapolation from a load at an elongation of 0.1% and a load at anelongation of 5%, and dividing the load at an elongation of 100% by thesectional area of the hollow fiber membrane.

[0053] A material for the hollow fiber membrane 3 a is not particularlylimited and includes polysulfones, polyether sulfones,polyacrylonitriles, polyimides, polyether imides, polyamides, polyetherketones, polyether ether ketones, polyethylenes, polypropylenes,poly(4-methylpentene)s, ethylene-vinyl alcohol copolymers, celluloses,cellulose acetates, poly(vinylidene fluoride)s,ethylene-tetrafluoro-ethylene copolymers, polytetrafluoroethylenes, etc.Composite materials thereof can also be used. Of the above-exemplifiedmaterials, the polyethylenes, poly-propylenes, ethylene-vinyl alcoholcopolymers, celluloses, poly(vinylidene fluoride)s and the like arepreferable because they can easily give a membrane having a modulus oftension in the above range.

[0054] As to the shape of the hollow fiber membrane, hollow fibermembranes having an inside diameter of 50 μm to 3,000 μm, preferably 500μm to 2,000 μm, and a ratio of inside diameter to outside diameter of0.3 to 0.8 are suitably used.

[0055] In addition, the hollow fiber membrane preferably has waves. Whenaccumulated materials adhering to the outer surfaces of the hollow fibermembranes are washed away by gas bubbling, the surfaces of the hollowfiber membranes are rubbed by contact between the hollow fiber membranesor contact of the hollow fiber membranes with the inner wall surface ofa housing, so that the water permeability is deteriorated in some cases.When the hollow fiber membrane has waves, the contact area can bereduced, so that the deterioration of the water permeability by therubbing can be markedly reduced. Furthermore, when the hollow fibermembrane has waves, the waves exhibit such an effect that theaccumulated materials washed away from the surfaces of the membranes areeasy to discharge from the bundle of the membranes.

[0056] The manner of the waving, i.e., the degree of the waving isexpressed in terms of the degree of crimping of the bundle of the hollowfiber membranes. The degree of crimping is preferably less than 2.5 andnot less than 1.5. When the degree of crimping is less than 1.5, thesuppression of the rubbing phenomenon and the discharge of theaccumulated materials are not sufficient. When the degree of crimping isnot less than 2.5, there arise disadvantages, for example, in that theoutside diameter of the bundle is increased, resulting in an increasedsize of the adhesion and fixation portions of the cartridge. The term“degree of crimping” used here means a value obtained by bundling 1,000hollow fiber membranes to put them in order, winding a PET film with athickness of 200 μm and a width of 40 mm having a spring balanceattached to the end of the film, around the bundle of the hollow fibermembranes, measuring the circumference of the bundle of the hollow fibermembranes while applying a load of 1 kg by pulling the spring balance,and calculating the value by the following equation:Degree  of  crimping = (circumference  [m]/Π)²/((outside  diameter  of  hollow  fiber  membrane  [m])² × number  of  hollow  fiber  memberanes)

[0057] In the cartridge of the present invention, the hollow fibermembranes are preferably fixed in a somewhat slacked state. The slackedstate is expressed in terms of the rate of slacking described below. Therate of slacking is preferably 0.1 to 10%, in particular, 1 to 5%. Whenthe rate of slacking is less than 0.1%, the vibration of the hollowfibers during gas bubbling is limited, so that the tendency of themembrane surface washing effect to diminish is strengthened. When therate of slacking is more than 10%, the distance between the hollow fibermembranes is uselessly increased, and hence the efficiency of contactwith bubbles is decreased, so that the membrane surface washing effecttends to be lessened.

[0058] The term “rate of slacking” means a percentage obtained bymeasuring the deflection distance L2 of the bundle of the hollow fibermembranes in a water-containing state which is due to the weight of thebundle itself, while keeping the cartridge horizontal, and dividing L2by the distance L1 between the adhesive interfaces (the surfaces on thecartridge center side) of the cartridge header and the bottom ring,respectively, which are fixed by means of the rods or pipes. The rate ofslacking is represented by the following equation:

Rate of slacking=(L2/L1)×100

[0059] As the adhesive used in the present invention, polymericmaterials such as epoxy resins, urethane resins, epoxyacrylate resins,silicone resins and the like are preferable. Of these, the urethaneresins are especially preferable because their reaction goes tocompletion in a relatively short time. In the cartridge head fixed bythe use of such an adhesive, the adhesion and fixation portion shouldhave such a pressure resistance that the adhesion and fixation portioncan withstand a differential pressure produced during use. For thispurpose, the adhesive preferably has a proper hardness. On the otherhand, the hollow fiber membranes are broken in some cases at theadhesive interfaces of the membranes by vibration during gas bubbling.This membrane breakage can be prevented by using an adhesive having aproper softness. Therefore, in order to impart a necessary andsufficient pressure resistance for use and prevent the membranebreakage, it is preferable to use an adhesive having such acharacteristic that it has a hardness of 30D to 70D in a workingtemperature range. The term “hardness” used here means a value measured10 seconds after pressing a Shore hardness meter against thesubstantially smooth surface of a sample. When this value is more than70D, the tendency of the membrane breakage to take place at the adhesiveinterface with the hollow fiber membranes is strengthened. When thevalue is less than 30D, the pressure resistance is not sufficient, sothat the adhesion and fixation portion is damaged causing leakage, insome cases.

[0060] As a method for the adhesion, well-known methods such ascentrifugal adhesion method, still-standing adhesion method and the likeare adopted. When the curing shrinkage and strength of the adhesive aredesired to be improved, a fibrous material such as glass fiber or carbonfiber, or fine powder of carbon black, alumina, silica or the like maybe incorporated into the above-exemplified adhesive.

[0061] Materials for the cartridge head 12, the bottom ring 13 and theconnecting rods or pipes 3 b which are used in the present invention arenot particularly limited and may be the same or different. Thermoplasticresins, stainless steel and composite materials such as fiber reinforcedplastic are preferably used as the materials.

[0062] As the thermoplastic resins, there are used polysulfones,polyether sulfones, polyimides, polyether imides, polyamides, polyetherketones, polyether ether ketones, polyethylenes, polypropylenes,poly(4-methylpentene)s, poly(vinylidene fluoride)s,ethylene-tetrafluoroethylene copolymers, polytetrafluoroethylenes,polycarbonates, acrylonitrile-butadiene-styrene copolymers (ABS resins),polyphenylene ethers, etc. As the stainless steel, SUS304, SUS316, etc.are used.

[0063] The cartridge head 12 serves not only as a fixation portion forsuspending the hollow fiber membrane cartridge 4 in a module housing fora tank type filtration apparatus or a rack type filtration apparatus butalso as a sealing portion for separation between raw water and filteredwater. Therefore, the cartridge head 12 is produced in a shape suitablefor the suspension, the fixation and the structure of a seal. Forexample, a level difference, a groove or a collar projecting outside inthe direction of diameter may be provided at the periphery of thecartridge head 12. Suitable examples of the shape of the cartridge headare shown in FIG. 9 to FIG. 11.

[0064] Although the shape of section in the direction of diameter of thecartridge head 12 may be round, square, hexagonal, oval or the like, itis preferably round from the viewpoint of sealing properties between thecartridge head 12 and an adhesion and fixation portion therefor and easeof production of a filtration tank.

[0065] The through-holes 14 a provided in the adhesion and fixationlayer 14 on the bottom ring side in the present invention are holes madein the adhesion and fixation layer itself. As to the size of thethrough-holes, their equivalent diameter ranges preferably from 2 mm to30 mm, in particular, from 5 mm to 25 mm. When the equivalent diameteris less than 2 mm, suspended materials in feed water adheres to thethrough-holes to plug them, in some cases. This tendency increasesparticularly in the treatment of water containing a high concentrationof suspended materials, such as water to be subjected to activatedsludge treatment. Therefore, the equivalent diameter is preferablyadjusted to 5 mm or more. When the equivalent diameter is more than 30mm, uniform introduction of bubbles into the whole bundle of themembranes becomes difficult, so that the efficiency of utilization of agas tends to be decreased. Here, the equivalent diameter is defined as4×(sectional area of flow path)/(circumference). The shape of thethrough-holes may be any of polygons (e.g. triangle, tetragon andhexagon), a round shape, an oval shape, a fan shape, a C shape, a starshape, etc.

[0066] Although the number of the through-holes is dependent on thesectional area of the cartridge and the number of fibers, it isapproximately 2 to 300, preferably 5 to 100, more preferably 10 to 60.

[0067] As to the location of the through-holes on a certain adhesion andfixation section, the through-holes should be in the bundle of thehollow fiber membranes. When the through-holes are located outside thebundle of the membranes, contact between bubbles rising from thethrough-holes and the hollow fiber membranes is not sufficient, so thatthe efficiency of utilization of a gas supplied is decreased. As to thelocation of the through-holes, it is especially preferable to dispersethe through-holes so that one or more hollow fiber membranes arecertainly present between one of the through-hole and at least one ofthe other through holes. It is more preferable to form many of thethrough-holes in the central portion of the bundle of the hollow fibermembranes. For example, it is preferable to form the through-holes sothat they are dispersed on the adhesion and fixation section at theintersections of multiplexed circles and radial lines, the intersectionsof lattices, or the apexes of a large number of equilateral triangles.FIG. 7 shows a case where the through-holes are radially located in thebundle of the membranes, and as to a certain through-hole, any of thehollow fiber membranes is not necessarily present between a certain pairof through-holes, but one or more of the hollow fiber membranes arepresent between another pair of through-holes. By providing suitablespaces among the through-holes by the location described above,suspended materials peeled off can be effectively discharged through afeed water inlet after gas bubbling, for example, in a module for racktype filtration apparatus. FIG. 8 shows a case where the through-holesare located so that one or more of the hollow fiber membranes arepresent between every pair of through-holes. By such location of thethrough-holes, the efficiency of utilization of a gas introduced can beincreased, so that a necessary washing effect can be obtained even bythe use of a small volume of a gas.

[0068] In the present invention, the bottom ring 13 preferably juts outbeyond the ends of the hollow fiber membranes 3 a to form a skirtportion, and is preferably fixed at the periphery of the bundle of thehollow fiber membranes to form a gas layer 14 b surrounded by theadhesion and fixation layer and the bottom ring. Although the length ofthe portion of the bottom ring 13 which juts out from the ends of thehollow fiber membranes is dependent on the diameter of the cartridge,the volume of a gas supplied and the diameter and number of thethrough-holes, it is preferably 5 mm to 200 mm for preventing dispersionand loss of the gas. When said portion is too long, the total length ofthe cartridge is undesirably long, resulting in the formation of auseless space. When said portion is too short, the gas supplied to thecartridge tends to be dispersed and lost in the lateral directionwithout being effectively introduced into the through-holes. It ispossible to open the bottom of the skirt portion and introduce a gasfrom below the bottom. It is also possible to join a removable lid forsealing the lower portion of the skirt portion, to the lower portion andintroduce a gas into the gas layer 14 b by joining a gas-supplying meansdirectly to the lid and/or the jutting-out portion forming the skirt.

[0069] The shape of section in the direction of diameter of the bottomring 13 may be round, square, hexagonal, oval or the like. When thecartridge is set in a filtration tank, the shape of section ispreferably the same as that of the cartridge head, and a round shape isespecially preferable as the shape of section.

[0070] The hollow fiber membrane cartridge of the present invention canbe produced as follows. A bundle of hollow fiber membranes whose hollowportions have been stopped at one end of the bundle and pipes forconnection and fixation are inserted into a cartridge head 12, and anadhesive is introduced into the cartridge head 12 to adhere and fix thehollow fiber membranes to one another and adhere and fix the pipes forconnection and fixation and the bundle of the hollow fiber membranes tothe cartridge head 12, so as not to permit the passage of liquid eitherin or out. The hollow fiber membranes and the adhesion and fixationlayer are cut together to open the ends of the hollow fiber membranes.

[0071] The other ends of the hollow fiber membranes are inserted into abottom ring together with the pipes for connection and fixation withoutstopping their hollow portions, and a predetermined rod, pipe or platefor forming through-holes 14 a is set in the bundle of the hollow fibermembranes. Then, an adhesive is introduced into the bottom ring 13 toadhere and fix the hollow fiber membranes to one another and adhere andfix the pipes for connection and fixation and the bundle of the hollowfiber membranes to the bottom ring 13. In this case, the hollow portionsat the ends of the hollow fiber membranes are sealed with the adhesiveat the same time. Thereafter, the rod, pipe or plate for formingthrough-holes 14 a is taken out of the adhesion and fixation layer toform through-holes 14 a.

[0072] The following is also possible: a rod, pipe or plate for formingthrough-holes 14 a is set in the bundle of the hollow fiber membranes,followed by adhesion and fixation, and the instrument for formingthrough-holes 14 a is taken out, after which a bottom ring 13 is fixedat the periphery of the adhesion and fixation layer by adhesion orwelding.

[0073] An example of tank type filtration apparatus (FIG. 1) comprisingthe hollow fiber membrane cartridges of the present invention suspendedand fixed therein is explained below.

[0074] In FIG. 1, numeral 1 denotes a tank type filtration apparatus forfiltering raw water fed, which can be used for water treatment inreducing turbidity and bacteria from a large volume of raw water such asriver water, lake water, underground water, sea water, life waste wateror industrial waste water.

[0075] The filtration tank 2 of the tank type filtration apparatus 1 iscomposed of a tank main body 2 a and a lid 2 b, and a partition plate 6is fixed on the inner wall of the tank main body 2 a at a predeterminedheight by welding or the like so as not to permit the passage of liquideither in or out. A feed water chamber 7 is formed of a space formed bythe tank main body 2 a and the partition plate 6. A treated waterchamber 10 is formed by the partition plate 6, the lid 2 b and a packing9.

[0076] As described above, the inside of the filtration tank 2 isdivided into the two chambers by the partition plate 6 fixed in thefiltration tank 2, and each hollow fiber membrane cartridge 4 of thepresent invention is suspended in the feed water chamber 7 with its oneend held by the partition plate 6.

[0077] The partition plate 6 holding the hollow fiber membrane cartridge4 suspended therefrom is made in a predetermined thickness so as to havea sufficient strength to withstand a load applied by the hollow fibermembrane cartridge and water pressure. A plurality of through-holes 6 afor inserting the hollow fiber membrane cartridges 4 are formed atpredetermined positions of the partition plate 6.

[0078] In the lower portion of each through-hole 6 a of the partitionplate 6, a projection 6 b jutting inside the through-hole 6 a in thedirection of the diameter is formed, and the lower end of the cartridgehead 12 provided at the periphery at the upper end of the hollow fibermembrane cartridge 4 is caught by the projection 6 b to suspend and holdthe hollow fiber membrane cartridge 4. As another embodiment, thefollowing is possible: a collar jutting outside-in the direction ofdiameter is formed on the cartridge head, and its underside is broughtinto contact with the top surface of the partition plate 6 through agasket to suspend and hold the hollow fiber membrane cartridge.

[0079] An O-ring 15 is fitted in a groove 6 c formed on the wall surfaceof each through-hole 6 a of the partition plate 6, and the outer wallsurface of the cartridge head 12 is bonded to the O-ring 15 by pressurewelding, whereby the cartridge head 12 is attached to the partitionplate 6 so as not to permit the passage of liquid either in or out. Agroove for fitting the O-ring 15 therein may be formed on the cartridgehead 12.

[0080] The upper edge face of the cartridge head 12 is moored by amooring member 16 which has been provided on the wall surface of eachthrough-hole 6 a of the partition plate 6 so as to be removable, wherebythe cartridge head 12 is fixed to the partition plate 6 and the hollowfiber membrane cartridge 4 is stably accommodated in the filtration tank2.

[0081] In the above structure, during filtration operation using thetank type filtration apparatus 1, raw water fed into the feed waterchamber 7 through a feed water inlet 2 c provided in the lower portionof the tank main body 2 a of the filtration tank 2 by means of a pump(not shown) fills up the feed water chamber 7 and is then conducted tothe peripheral surface of each hollow fiber membrane 3 a.

[0082] The raw water near the periphery of each hollow fiber membrane 3a is filtered under pressure through the hollow fiber membrane 3 a fromthe outside to the inside, and the filtered water is introduced into thetreated water chamber 10 through the opened upper end of the hollowfiber membrane 3 a. The filtered water accommodated in the treated waterchamber 10 is taken out of the filtration tank 2 through a treated wateroutlet 2 d provided in the upper portion of the lid 2 b.

[0083] As another operation method, a method can be adopted whichcomprises carrying out filtration by sucking air in the treated waterchamber 10 through the treated water outlet 2 d by means of a suctionpump (not shown) to reduce the pressure, while filling the feed waterchamber 7 with raw water.

[0084] When the hollow fiber membranes 3 a are subjected to back washingwith the filtered water, the filtered water is supplied through thetreated water outlet 2 d and allowed to flow backward into the feedwater chamber 7 to remove suspended materials (materials incapable ofpermeating the membranes) accumulated on the outer walls of the hollowfiber membranes 3 a, after which it is discharged from the filtrationtank 2 through the feed water inlet 2 c.

[0085] When the hollow fiber membranes 3 a are subjected to gasbubbling, a gas is supplied at first to the feed water chamber 7 througha gas inlet 2 f provided in the lower portion of the tank main body 2 a,with the feed water chamber 7 filled with raw water. The gas flows asbubbles into the feed water chamber 7 filled with the raw water, througha nozzle 5 a, and passes through each bottom ring 13 and then thethrough-holes 14 a of the adhesion and fixation layer 14 to vibrate thehollow fiber membranes 3 a. Thus, the gas peels off the suspendedmaterials adhering to the surfaces of the hollow fiber membranes 3 a.Gas accumulated in the upper portion of the feed water chamber 7 isdischarged from the filtration tank 2 through a gas outlet 2 g providedin the upper portion of the tank main body 2 a. In the above-mentionedgas bubbling, since the adhesion and fixation layer 11 on the cartridgehead side and the adhesion and fixation layer 14 on the bottom ring sideare connected and fixed to each other by means of a stainless steel pipe3 b in the hollow fiber membrane cartridge 4, the bottom ring 13 isneither lifted nor displaced from a position corresponding to the nozzle5 a irrespective of the flow rate of the gas, so that satisfactorywashing can be carried out.

[0086] In the above gas bubbling operation, for example, air, nitrogengas or oxygen gas is supplied at first, with the feed water chamber 7filled with the raw water, namely, with the raw water being at rest andstaying in the feed water chamber 7. After gas bubbling, theabove-mentioned back washing operation is carried out to wash away thesuspended materials peeled off as described above, with filtered watersupplied through the treated water outlet 2 d. The filtered watercontaining the suspended materials peeled off is discharged from thefiltration tank 2 through the feed water inlet 2 c and accommodated in awaste water tank (not shown).

[0087] Either the gas bubbling operation or the back washing operationmay be carried out first. They may also be carried out at the same time.When the back washing and the gas bubbling are carried out at the sametime, rubbing of the surfaces of the membranes, which is apt toaccompany the vibration of the hollow fiber membranes, can be desirablyprevented. The frequencies of the above-mentioned back washing operationand gas bubbling operation are preferably determined while monitoringthe stability of the filtration operation.

[0088] Next, an example of tank type filtration apparatus (FIG. 4)comprising the hollow fiber membrane cartridges suspended from and fixedto a treated water header piping is explained below.

[0089] In FIG. 4, each hollow fiber membrane cartridge 4 is suspendedfrom and fixed to a branch pipe 18 branched from a treated water headerpiping 17, by the use of a cartridge head collar 12 a provided at theperiphery of the cartridge head 12 and a cramp 20 through a gasket 19.

[0090] In the above structure, during filtration operation using thetank type filtration apparatus 1, raw water fed into a feed waterchamber 7 through a feed water inlet 2 c provided in the lower portionof the tank main body 2 a of a filtration tank 2 by means of a pump (notshown) fills up the feed water chamber 7 and is then conducted to theperipheral surface of each hollow fiber membrane 3 a. The raw water nearthe periphery of each hollow fiber membrane 3 a is filtered underpressure through the hollow fiber membrane 3 a from the outside to theinside, and the filtered water is introduced into the treated waterheader piping 17 through the opened upper end of the hollow fibermembrane 3 a and the branch pipe 18. The filtered water in the treatedwater header piping is discharged from the filtration tank 2 through atreated water outlet 2 d provided in the tank main body 2 a.

[0091] The concentrated water not filtered through the hollow fibermembranes 3 a is discharged from the filtration tank 2 through theconcentrated water outlet 2 g of a lid 2 b provided in the upper portionof the filtration tank 2.

[0092] When the hollow fiber membranes 3 a are subjected to back washingwith the filtered water, the filtered water is supplied through thetreated water outlet 2 d and allowed to flow backward into the feedwater chamber 7 to remove suspended materials (materials incapable ofpermeating the membranes) accumulated on the outer walls of the hollowfiber membranes 3 a, after which it is discharged from the filtrationtank 2 through the concentrated water outlet 2 g.

[0093] When the hollow fiber membrane cartridges 4 are subjected to gasbubbling, a gas is supplied at first to the feed water chamber 7 througha gas inlet 2 f provided in the lower portion of the tank main body 2 a,with the feed water chamber 7 filled with raw water. The gas flows asbubbles into the feed water chamber 7 through a nozzle 5 a and isconducted to the side of the periphery of each hollow fiber membrane 3 afrom the bottom ring 13 through the through-holes 14 a of the adhesionand fixation layer 14 to stir water in the bundle of the hollow fibermembranes 3 a and vibrate the hollow fiber membranes 3 a. Thus, the gaspeels off the suspended materials adhering to the surfaces of the hollowfiber membranes 3 a. The gas that has vibrated the hollow fibermembranes 3 a is discharged from the filtration tank 2 through theconcentrated water outlet 2 g provided in the lid 2 b.

[0094] Either the above-mentioned gas bubbling operation or theabove-mentioned back washing operation may be carried out first. Theymay also be carried out at the same time. When the back washing and thegas bubbling are carried out at the same time, rubbing of the surfacesof the membranes, which is apt to accompany the vibration of the hollowfiber membranes, can be desirably prevented. The frequencies of theabove-mentioned back washing operation and gas bubbling operation arepreferably determined while monitoring the stability of the filtrationoperation.

[0095] In the above-mentioned gas bubbling, since the adhesion andfixation layer 11 on the cartridge head side and the adhesion andfixation layer 14 on the bottom ring side are connected and fixed toeach other by means of a SUS pipe 3 b in the hollow fiber membranecartridge 4, the bottom ring 13 is neither lifted nor displaced from aposition corresponding to the nozzle 5 a irrespective of the flow rateof the gas, so that satisfactory washing can be carried out.

[0096] Next, an example of module for rack type filtration apparatus(FIGS. 5 and 6) comprising the hollow fiber membrane cartridge of thepresent invention suspended and fixed therein is explained below. Theterm “module” used herein means an assembly comprising a housing havingat least a feed water inlet and an open-ended portion provided in theupper portion of the housing and a hollow fiber membrane cartridge,wherein the hollow fiber membrane cartridge is inserted in the housingand fixed to the open-ended portion in the upper portion of the housingso as to be removable and so as not to permit the passage of liquideither in or out.

[0097] The housing 21 a has the feed water inlet 2 c in the lowerportion and a housing head 21 b fitted with a concentrated water nozzle22, in the upper portion. The housing head has a double-pipe structurein which the inner wall of the housing head has head openings thatcommunicate with the concentrated water nozzle 22 through a space formedinside the outer wall by the inner wall and the outer wall. Thecartridge is accommodated inside the inner wall.

[0098] The hollow fiber membrane cartridge of the present invention isinserted into the housing from above and fixed to the upper end of thehousing head by means of the collar 12 a of the cartridge through agasket or an O-ring so as not to permit the passage of liquid either inor out. The collar 12 a of the cartridge and a cap having a treatedwater outlet 2 d are fixed to each other through an O-ring 25 so as notto permit the passage of liquid either in or out. The housing head 21 b,the collar 12 a and the cap 24 are integrally fixed by means of ahousing nut 23.

[0099] In the above structure, during filtration operation using a racktype filtration apparatus, raw water fed into the housing 21 a through afeed water piping (not shown) and the feed water inlet 2 c by means of apump fills to the bottom ring 13 and is then conducted to the peripheralsurface of each hollow fiber membrane 3 a through the through-holes 14a.

[0100] The raw water near the periphery of each hollow fiber membrane 3a is filtered under pressure through the hollow fiber membrane 3 a fromthe outside to the inside, and the filtered water is introduced into thecap 24 through the opened upper end of the hollow fiber membrane 3 a.The filtered water introduced into the cap 24 is taken out of the racktype apparatus through the filtered water piping (not shown) of the racktype apparatus and a treated water outlet 2 d. The raw water conductedto the peripheral surface of each hollow fiber membrane 3 a can bepartly conducted to the concentrated water nozzle 22 through the headopenings 27 to be returned to the circulation tank or raw water tank(not shown) of the apparatus through a concentrated water outlet 2 g.

[0101] When the hollow fiber membranes 3 a are subjected to back washingwith the filtered water, the filtered water is supplied through thetreated water outlet 2 d and allowed to flow backward into the housing21 a to remove suspended materials (materials incapable of permeatingthe membranes) accumulated on the outer walls of the hollow fibermembranes 3 a, after which it is discharged from the housing 21 athrough the head openings 27 and the concentrated water nozzle 22. It isalso possible to discharge the water containing the suspended materialswhich has been obtained by the washing with the filtered water allowedto flow backward, through the through-holes 14 a present in the bottomring 13 and the feed water outlet 2 c in the lower portion.

[0102] When the hollow fiber membranes 3 a are subjected to gasbubbling, a gas is supplied at first to the bottom ring 13 through a gasinlet (not shown) provided in a piping connected to the feed water inlet2 c from below, with the housing 21 a filled with raw water or thefiltered water. The gas supplied passes through the through-holes 14 aof the adhesion and fixation layer 14 while staying in the skirt portionprovided in the lower portion of the bottom ring 13, to vibrate thehollow fiber membranes 3 a. Thus, the gas peels off the suspendedmaterials adhering to the surfaces of the hollow fiber membranes 3 a. Itis also possible to carry out the above-mentioned back washingsimultaneously with the gas bubbling and discharge the washings from thehousing through the concentrated water nozzle 22. In this case, rubbingof the surfaces of the membranes, which is apt to accompany thevibration of the hollow fiber membranes, can be desirably prevented.

[0103] Then, flushing may be carried out if necessary. The term“flushing” used here means a step of discharging the suspended materialspeeled off by the above-mentioned gas bubbling, from the housing. Theflushing is usually carried out by introducing raw water through thefeed water inlet 2 c and discharging the same through the concentratedwater nozzle 22.

[0104] In the above-mentioned gas bubbling, since the adhesion andfixation layer 11 on the cartridge head side and the adhesion andfixation layer 14 on the bottom ring side are connected and fixed toeach other by means of a stainless steel pipe 3 b in the hollow fibermembrane cartridge 4, the bottom ring 13 is not lifted irrespective ofthe flow rate of the gas, so that satisfactory washing can be carriedout.

[0105] Specific examples concerning the cartridge of the presentinvention are described below.

[0106] Hollow Fiber Membrane A

[0107] In a Henschel mixer, 23 wt % of hydrophobic silica having anaverage primary-particle size of 0.016 μm and a specific surface area of110 m²/g (Aerosil R-970, a trade name, mfd. by Nippon Aerosil Co.,Ltd.), 30.8 wt % of dioctyl phthalate and 6.2 wt % of dibutyl phthalatewere mixed, followed by adding thereto 40 wt % of PVdF having a weightaverage molecular weight of 242,000 (Kureha KF Polymer #1000, a tradename, mfd. by Kureha Chemical Industry Co., Ltd.), and they were mixedagain in the Henschel mixer.

[0108] The resulting mixture was shaped into hollow fibers bymelt-extruding the mixture into a water bath at 40° C. through the airat a rate of 20 m/min by using a hollow-fiber producing apparatusobtained by fitting a hollow-fiber-shaped spinning hole to a 30-mmφtwin-screw extruder. The shaped product was continuously taken off at arate of 20 m/min with a sponge belt type take-off machine havingvariable gaps, passed through a heating bath controlled at a spacetemperature of 40° C., and then taken off at a rate of 40 m/min with thesame take-off machine as above to be stretched at a ratio of 2.0. Theresulting hollow fiber membranes were passed through a heating bathcontrolled at a space temperature of 80° C., and cooled by theircontinuous holding between a pair of uneven rolls located on the surfaceof water in a cooling water bath, after which the stretched fibers weretaken off at a rate of 30 m/min with a sponge belt type take-off machineto be shrunk to 1.5 times the original length of the hollow fibers, andwere wound up as a hank.

[0109] Subsequently, the immersion of the wound-up hollow fibermembranes in methylene chloride at 30° C. for 1 hour was repeated threetimes to extract dioctyl phthalate and dibutyl phthalate from themembranes, and then the membranes were dried. Thereafter, the hollowfiber membranes were immersed in a 50% aqueous ethanol solution for 30minutes and then in water for 30 minutes to be wetted with water, afterwhich their immersion in a 5% aqueous sodium hydroxide solution at 40°C. for 1 hour was repeated twice to extract hydrophobic silica from themembranes, and the membranes thus treated were washed with warm water at60° C. for 12 hours and then dried.

[0110] The hollow fiber membranes thus obtained had an outside diameterof 1.25 mm, an inside diameter of 0.65 mm, a permeability to pure waterof 6,000 liters/m²/hour/0.1 MPa, a modulus in tension of 19.6 MPa, and adegree of crimping of 1.68.

[0111] Hollow Fiber Membrane B

[0112] The above-mentioned hollow fiber membranes A were heat-treated inan oven at 140° C. for 2 hours. The resulting hollow-fiber membranes hadan outside diameter of 1.24 mm, an inside diameter of 0.65 mm, apermeability to pure water of 5,300 liters/m²/hour/0.1 MPa, a modulus intension of 40.2 MPa, and a degree of crimping of 1.72.

[0113] Hollow Fiber Membrane C

[0114] By the process described in International Publication NumberWO00/63122, the hollow fiber membranes made of PVdf of Example 1 in thisreference were produced. These hollow fiber membranes had a modulus intension of 77.3 MPa and waves corresponding to a degree of crimping of1.74.

[0115] Hollow Fiber Membrane D

[0116] By the process described in International Publication NumberWO97/03677, the hollow fiber membranes made of a polysulfone of Example1 in this reference were produced. These hollow fiber membranes had amodulus in tension of 100 MPa, were straight without a wave and had adegree of crimping of 1.45.

[0117] Hollow Fiber Membrane E

[0118] By the process described in JP-A-03-42025, the hollow fibermembranes made of a polyethylene of Example 1 in this reference wereproduced. These hollow fiber membranes had a modulus in tension of 50MPa, were straight without waves and had a degree of crimping of 1.47.

EXAMPLE 1

[0119] Using 6,400 of the above-mentioned hollow fiber membranes B, acartridge was produced which was composed of the cartridge head having aflat type collar and shown in FIG. 10, the bottom ring having twenty-six11-mmφ through-holes and a projection with a length of 40 mm and shownin FIG. 8, and two stainless steel pipes with an outside diameter of 10mm and a thickness of 1 mm. The pipes were located at outermostpositions in a bundle of the hollow fiber membranes as shown in FIG. 8and were adhered and fixed to the hollow fiber membranes by the use of atwo-pack thermosetting urethane resin (SA-6330A2/SA-6330B5, a tradename, mfd. by SUNYURECK). The cartridge head and the bottom ring werethose made of ABS, and the adhesive used had Shore hardness values at 5°C. and 40° C. of 65D and 40D, respectively.

[0120] The outside diameters of the cartridge head and the bottom ringwere 167 mm and 150 mm, respectively. The adhesive thicknesses in thecartridge head and the bottom ring were 65 mm and 30 mm, respectively.The effective length of the hollow fiber membranes was 2,010 mm and therate of slacking of the membranes was 4%.

[0121] The cartridge could easily be carried by holding the two pipes.

[0122] The cartridge was accommodated in the housing shown in FIG. 5,and a cap was joined to the cartridge and the housing by the use of ahousing nut. In the joining, as shown in FIG. 10, the cap was fixed withtwo O-rings inserted between the housing and cap and the cartridge head,so as not to permit the passage of liquid either in or out.

[0123] The module described above was set in a rack type apparatus and afiltration test using water of the Fuji River as raw water was carriedout. The operation conditions are described below.

[0124] Volume of water filtered: 2.7 m³/m²/day.

[0125] Volume of water concentrated: one-half the volume of waterfiltered.

[0126] Volume of water used for back washing: 1.5 times the volume ofwater filtered.

[0127] Gas (air) flow rate: 0.3 ml/sec/fiber membrane

[0128] Volume of water used for flushing: 2 m³/hour.

[0129] Operation cycle: filtration 28.5 min.−back washing/gas bubbling(at the same time) 1 min.−flushing 0.5 min.

[0130] In the back washing, water for back washing was supplied afteradding sodium hypochlorite thereto in a proportion of 4 mg/liter.

[0131] During the operation, the trans membrane pressure (in terms ofits value at 20° C.; the same applied in the other examples) after theback washing increased gradually and reached 40 kPa 48 hours after theback washing. Thereafter, it became stable and was 40 to 45 kPa even1,000 hours after the back washing.

[0132] The water temperature during the operation was 8° C. to 13° C.,and the average turbidity was 3 ppm.

[0133] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no abnormality inthem.

EXAMPLE 2

[0134] A cartridge was produced in the same manner as in Example 1except for using hollow fiber membranes C and the cartridge head havinga ferrule type collar and shown in FIG. 9. The rate of slacking of thehollow fiber membranes in the cartridge was 2%.

[0135] The hollow fiber membrane cartridge was set in the tank typeapparatus shown in FIG. 4 and a filtration experiment was carried out.The operation conditions are described below.

[0136] Volume of water filtered: 2.4 m³/m²/day.

[0137] Volume of water concentrated: one-half the volume of waterfiltered.

[0138] Volume of water used for back washing: 1.5 times the volume ofwater filtered.

[0139] Gas (air) flow rate: 0.3 ml/sec/fiber membrane

[0140] Volume of water used for flushing: 3 m³/hour.

[0141] Operation cycle: filtration 28 min.−back washing/gas bubbling (atthe same time) 1 min.−flushing 1 min.

[0142] In the back washing, water for back washing was supplied afteradding sodium hypochlorite thereto in a proportion of 4 mg/liter.

[0143] During the operation, the trans membrane pressure after the backwashing increased gradually and reached 60 kPa 48 hours after the backwashing. Thereafter, it became stable and was 65 to 70 kPa even 1,000hours after the back washing.

[0144] The water temperature during the operation was 12° C. to 16° C.,and the average turbidity was 3 ppm.

[0145] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no abnormality inthem.

EXAMPLE 3

[0146] A cartridge was produced in the same manner as in Example 1except for using hollow fiber membranes A, the cartridge head having aferrule type collar and shown in FIG. 9, and four 10-mmφ fiberreinforced plastic round rods. The round rods were located at theoutermost positions, respectively, corresponding to one-fourth thecircumference of a bundle of the hollow fiber membranes. The rate ofslacking of the hollow fiber membranes in the cartridge was 5%.

[0147] The cartridge could easily be carried by holding two of the roundrods which faced each other.

[0148] A filtration experiment using a tank type filtration apparatuswas carried out in the same manner as in Example 2.

[0149] During the operation, the trans membrane pressure after the backwashing increased gradually and reached 40 kPa 48 hours after the backwashing. Thereafter, it became stable and was 40 to 45 kPa even 1,000hours after the back washing.

[0150] The water temperature during the operation was 14° C. to 18° C.,and the average turbidity was 3 ppm.

[0151] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no abnormality inthem.

EXAMPLE 4

[0152] A cartridge was produced in the same manner as in Example 1except for using the cartridge head having a thread and shown in FIG.11, changing the length of the projection of the bottom ring to 100 mm,and using a two-pack thermosetting urethane resin (SA-6330A2/SA-6330B4,a trade name, mfd. by SUNYU REC Co., Ltd.) as an adhesive. This adhesivehad Shore hardness values at 5° C. and 40° C. of 52D and 35D,respectively. The rate of slaking of the hollow fiber membranes in thecartridge was 4%.

[0153] Suction filtration was carried out by connecting the hollow fibermembrane cartridge to a piping as shown in FIG. 11 and immersing thesame in a raw-water tank. In the projection of the bottom ring of thecartridge, a through-hole was provided at a distance of 10 mm from thelower end of the projection, and a nozzle for air supply was insertedinto this through-hole and fixed, so that air could be supplied to theinside of the skirt. The operation conditions are described below.

[0154] Volume of water filtered: 2.7 m³/m²/day.

[0155] Volume of water used for back washing: 1.5 times the volume ofwater filtered.

[0156] Gas (air) flow rate: 0.3 ml/sec/fiber membrane

[0157] Operation cycle: filtration 18 min.−back washing/gas bubbling (atthe same time) 1 min.−drainage 0.5 min.−raw water feed 0.5 min.

[0158] (That is, in the cycle, filtration was carried out for apredetermined time, and then back washing and gas bubbling were carriedout at the same time, after which the liquid in the raw-water tank wasdischarged from the tank, and raw water was fed to the raw-water tank tofill up the tank, followed by the start of filtration.)

[0159] During the filtration, raw water was continuously fed to theraw-water tank in the same volume as that of water filtered. In the backwashing, water for back washing was supplied after adding sodiumhypochlorite thereto in a proportion of 4 mg/liter.

[0160] During the operation, the amount of reduced pressure by suctionafter the back washing increased gradually and reached 50 kPa 48 hoursafter the back washing. Thereafter, it became stable and was 50 to 55kPa even 1,000 hours after the back washing.

[0161] The water temperature during the operation was 12° C. to 16° C.,and the average turbidity was 5 ppm.

[0162] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no abnormality inthem.

EXAMPLE 5

[0163] A cartridge was produced in the same manner as in Example 4except for locating two hundreds (200) 3-mmφ-through-holes uniformly inthe bundle of the hollow fiber membranes in the bottom ring. The rate ofslacking of the hollow fiber membranes in the cartridge was 4%.

[0164] A filtration experiment was carried out in the same manner as inExample 4. The water temperature during the operation was 12° C. to 16°C., and the average turbidity was 5 ppm.

[0165] During the operation, the amount of reduced pressure by suctionafter the back washing increased gradually and reached 50 kPa 48 hoursafter the back washing. Thereafter, it became stable and was 55 kPa 500hours after the back washing. Then, it tended to increase gradually butwas 65 kPa even 1,000 hours after the back washing.

[0166] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no particularabnormality in them.

EXAMPLE 6

[0167] A cartridge was produced in the same manner as in Example 2except for changing the outside diameters of the cartridge head and thebottom ring to 90 mm and 78 mm, respectively, changing the adhesivethicknesses in the cartridge head and the bottom ring to 30 mm and 20mm, respectively, using 1,600 hollow fiber membranes B, and using atwo-pack thermosetting urethane resin (KC-374/KN-575, a trade name, mfd.by Nippon Polyurethane Industry Co., Ltd.) as an adhesive. Sixthrough-holes were located at positions that were 19 mm apart from thecenter of the bottom ring and corresponded to one-sixth thecircumference of the bottom ring. The adhesive had Shore hardness valuesat 5° C. and 40° C. of 50D and 38D, respectively. The effective lengthof the hollow fiber membranes in the cartridge was 940 mm and the rateof slaking of the hollow fiber membranes in the cartridge was 3%.

[0168] The hollow fiber membrane cartridge was set in the tank typeapparatus shown in FIG. 4 and a filtration experiment was carried out.The operation conditions are described below.

[0169] Volume of water filtered: 2.4 m³/m²/day.

[0170] Volume of water concentrated: one-half the volume of waterfiltered.

[0171] Volume of water used for back washing: 1.5 times the volume ofwater filtered.

[0172] Gas (air) flow rate: 0.2 ml/sec/fiber membrane

[0173] Volume of water used for flushing: 0.7 m³/hour.

[0174] Operation cycle: filtration 28 min.−back washing/gas bubbling (atthe same time) 1 min.−flushing 1 min.

[0175] In the back washing, water for back washing was supplied afteradding sodium hypochlorite thereto in a proportion of 4 mg/liter.

[0176] During the operation, the trans membrane pressure after the backwashing increased gradually and reached 50 kPa 48 hours after the backwashing. Thereafter, it became stable and was 55 to 60 kPa even 1,000hours after the back washing.

[0177] The water temperature during the operation was 12° C. to 16° C.,and the average turbidity was 3 ppm.

[0178] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no abnormality inthem.

EXAMPLE 7

[0179] A cartridge was produced in the same manner as in Example 6except for using hollow fiber membranes D. The rate of slacking of thehollow fiber membranes in the cartridge was 0.5%.

[0180] A filtration experiment was carried out in the same manner as inExample 6.

[0181] During the operation, the trans membrane pressure after the backwashing increased gradually and reached 40 kPa 48 hours after the backwashing. Thereafter, it increased gradually and reached 90 kPa 500 hoursthe back washing and then 140 kPa 1,000 hours after the back washing.

[0182] The water temperature during the operation was 12° C. to 16° C.,and the average turbidity was 3 ppm.

[0183] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no abnormality inthem.

EXAMPLE 8

[0184] A cartridge was produced in the same manner as in Example 1except for using hollow fiber membranes E. The rate of slacking of thehollow fiber membranes in the cartridge was 3%.

[0185] A filtration experiment was carried out in the same manner as inExample 1.

[0186] During the operation, the trans membrane pressure after the backwashing increased and reached 80 kPa 48 hours after the back washing.Thereafter, it increased gradually and reached only 100 kPa 500 hoursafter the back washing and then only 130 kPa 1,000 hours after the backwashing.

[0187] The water temperature during the operation was 12° C. to 10° C.,and the average turbidity was 3 ppm.

[0188] After 1,000 hours of the operation, the cartridge was taken outand the hollow fiber membranes and the adhesion and fixation portions ofthe cartridge were observed to find that there was no abnormality inthem.

EXAMPLE 9

[0189] A cartridge was produced in the same manner as in Example 1, andan acceleration test for evaluating the durability of the cartridge ingas bubbling was carried out. The same operation cycle as in Example 1was employed except for changing the filtration time in the filtrationoperation in Example 1 to 2 minutes. The operation was carried out in aclosed system by returning filtered water, concentrated water andwashing water for back washing to a raw-water tank. The watertemperature in the system was maintained at 5° C. by cooling on theassumption that the operation is carried out in thelow-water-temperature season.

[0190] After repeating a cycle consisting of filtration, backwashing/gas bubbling and flushing for a period corresponding to 5 yearsin the case of employing the operation cycle described in Example 1, thecartridge was taken out and observed to find that there was noabnormality in the hollow fiber membranes, the adhesion and fixationportions of the cartridge head, and the like.

COMPARATIVE EXAMPLE 1

[0191] A cartridge was produced in the same manner as in Example 2except for employing the bottom ring structure shown in FIG. 4 and FIG.6 in JP-A-10-137552, locating a 25-mmφ PVC pipe in the center of thecartridge and using hollow fiber membranes D. The through-holes of thebottom ring are open at a distance of 5 mm from the PVC pipe located inthe center and had a width of 10 mm. The area occupied by a bundle ofthe hollow fiber membranes was the same as in Example 2. The rate ofslacking of the hollow fiber membranes in the cartridge was 0.5%.

[0192] Since the middle of the cartridge could not be held, two personsunavoidably carried the cartridge by holding the cartridge head and thebottom ring, respectively.

[0193] When the same filtration test as in Example 2 was carried out byusing said cartridge, the intermembranous differential pressure afterthe back washing increased rapidly and reached 300 kPa 400 hours afterthe back washing, so that the operation was unavoidably discontinued.

COMPARATIVE EXAMPLE 2

[0194] A cartridge was produced in the same manner as in Example 1except for using a two-pack thermosetting urethane resin(Coronate-4403/Nipporan-4221, a trade name, mfd. by Nippon PolyurethaneIndustry Co., Ltd.) as an adhesive. The adhesive had Shore hardnessvalues at 5° C. and 40° C. of 72D and 28D, respectively.

[0195] An acceleration test for evaluating the durability of thecartridge in gas bubbling was carried out in the same manner as inExample 9 to find that the hollow fiber membranes were broken at theiradhesive interfaces to cause leakage, at a point of time correspondingto one year of repetition of the operation cycle described in Example 1.

[0196] Industrial Applicability

[0197] The present inventive cartridge, module for rack type filtrationapparatus using said cartridge, and tank type filtration apparatus usingsaid cartridge permit long-term stable filtration operation because theymaximize the extension and/or vibration of each hollow fiber membraneduring washing by gas bubbling to facilitate peeling-off of suspendedmaterials accumulated on the outer surfaces of the hollow fibermembranes, even by introduction of a small volume of a gas, and permiteasy discharge of the peeled-off suspended materials from the hollowfiber membrane cartridge. Furthermore, the cartridge of the presentinvention is very useful for practical purposes because it has asufficient durability for practical purposes and it is easy to handle,for example, when carried. The module for filtration apparatus and thetank type filtration apparatus which use said cartridge are economicalbecause a housing or a tank, respectively, can be repeatedly usedtherein even when the cartridge is replaced by a fresh one.

1. A hollow fiber membrane cartridge comprising a bundle of a pluralityof hollow fiber membranes, both ends of which are fixed by adhesion inadhesion and fixation layers, respectively, a cartridge head fixed atperiphery of the bundle at one end so as not to permit passage of liquideither in or out, and a bottom ring fixed at periphery of the bundle atthe other end so as not to permit passage of liquid either in or out,which is characterized in that said cartridge head and said bottom ringare connected and fixed to a plurality of rods or pipes, the hollowportion at the end of each hollow fiber membrane on the cartridge headside is open, the hollow portion at the end of each hollow fibermembrane on the bottom ring side is sealed, and a plurality ofthrough-holes are provided in the adhesion and fixation layer on thebottom ring side and are located in the bundle of the hollow fibermembranes.
 2. A hollow fiber membrane cartridge according to claim 1,wherein the end of said bottom ring juts out beyond the ends of thehollow fiber membranes.
 3. A hollow fiber membrane cartridge accordingto claim 1 or claim 2, wherein said cartridge head has a collar at itsperiphery.
 4. A hollow fiber membrane cartridge according to any one ofclaims 1 to 3, wherein at least one of said rods or pipes is locatednear the periphery of the bundle of the hollow fiber membranes.
 5. Ahollow fiber membrane cartridge according to claim 4, wherein said rodsor pipes are connected and fixed to said cartridge head and said bottomring by adhesion to them together with the hollow fiber membranes in theadhesion and fixation layers.
 6. A hollow fiber membrane cartridgeaccording to any one of claims 1 to 5, wherein the hollow fibermembranes have waves.
 7. A hollow fiber membrane cartridge according toany one of claims 1 to 6, wherein the modulus in tension of the hollowfiber membrane is less than 90 MPa and not less than 10 MPa.
 8. A hollowfiber membrane cartridge according to claim 7, wherein the modulus intension of the hollow fiber membrane is not more than 70 MPa and notless than 10 MPa.
 9. A hollow fiber membrane cartridge according to anyone of claims 1 to 8, wherein the hollow fiber membranes are in aslacked state and the rate of slacking is not more than 10% and not lessthan 0.1%.
 10. A hollow fiber membrane cartridge according to any one ofclaims 1 to 9, wherein the plurality of said through-holes provided inthe adhesion and fixation layer on the bottom ring side are located sothat the hollow fiber membranes are present among the through-holes. 11.A hollow fiber membrane cartridge according to any one of claims 1 to10, wherein said plurality of through-holes provided in the adhesion andfixation layer on the bottom ring side have an inside diameter of 2 to30 mm.
 12. A hollow fiber membrane cartridge according to any one ofclaims 1 to 11, wherein an adhesive constituting said adhesion andfixation layers is a urethane resin having such a characteristic thatits hardness is 70D to 30D in a working temperature range.
 13. A modulefor rack type filtration apparatus using a hollow fiber membranecartridge according to any one of claims 1 to
 12. 14. A tank typefiltration apparatus using a hollow fiber membrane cartridge accordingto any one of claims 1 to
 12. 15. A tank type filtration apparatusaccording to claim 14, wherein said hollow fiber membrane cartridge issupported in a suspended state.